I certainly have not had one sit around for twenty years, but i did an Imperial Stout that was about 9% abv that sat around for about 18 months. Even in that time, the hops almost vanished and it was like 85 IBU.

I would actually aim for this to be something that is so high ABV and IBU that it seems undrinkable for a year or two and by the 20 year mark it might mellow into an incredible beer.

That's pretty much what i was thinkign bassbone, make something 10% plus and with so much hops you wouldnt think of drinking it for a few years...this might get me closer to 5 or 10, but i reckon 20 will be one hell of a stretch.

I'll find that Radical Brewing book, I liked that idea, thanks. Excellent tips on the choices of hops as well!

I'll post a recipe (i want to do about 13gallons) when i find a decent one, with enough hops.

you know, this same idea had popped into my head periodically... as i do not have any children, it gives me planning time! great idea though if you're doing a 13 gallon batch, it'd be good to see if you can pop one every year or so to see where its going. or hell, do 2 different. like barely wine and a stout?

High alcohol and hops are both preservative. Should work well. Aim for 12%+ and 100+IBU.
I'm planning on doing the same thing. My son's just about 1 year old and I tried a 0.120 barleywine shortly after he was born. Unfortunately I bottled too soon and ended up with spouters. I had to dump them. I'm going to try again the week before his birthday.

Since the legal drinking age is 19 here, here's my 0.119 OG and 119 IBU recipe: